func_plat has backwards mins/maxs errors when using negative height

[SamVanheer]

func_plat has backwards mins/maxs errors when using negative height.

The fgd claims height can be negative but because of how func_plat_trigger calculates its bounding box a negative height will result in that error.

It should be as easy as swapping the min and max x y and z bounds to make them valid to fix this error.